Characteristics of trans-critical propane spray discharged from multi-hole GDI injector

The results show that the trans-critical spray has longer vapor penetration and shorter liquid penetration than the flash boiling spray, but those two sprays have similar curve liquid boundaries near the nozzle. Several discernable collapsed shock structures near the nozzle are observed at Tf = 120 °C, pf=120 bar, pa = 1 bar, but they disappear when pf drops to 60 bar for the transition path may not enter the two-phase region, and the liquid phase hardly occurs. The Mach disk distance of trans-critical spray in this study is larger than that of the under-expanded ideal gas jet because of the collapse phenomenon. At Tf = 120 °C, pf = 120 bar, the liquid length decreases when paincreases from 0.2 bar to 2.5 bar and increases when pa continues to rise.